The angle (with respect to a wall) from which a ball, rolled across the floor, hits a wall is the same as the angle (with respect to the wall) of bouncing off.

Children can experiment with rolling a ball on the floor towards a wall, starting at various angles, and observe where the ball goes after hitting the wall.

A booklet would show the various angles of rolling the ball along the floor toward the wall and the (equal) angles of bouncing off.